Selective radio reception



I M 9 -v .1. H HAMMOND, JR

SELECTIVE RADIQ RECEPTION s Sheet-Sheet 1 Filed Nov. 9, 1929 N wm $4 AAAA INVENTOR JOHN HAYS HAMMOND JR. BY 7 Y WPW ATTORNEY March 7, 1933. J HHAMMOND, JR 1,900,283

SELECTIVE RADIO RECEPTION Filed Nov. 9, 1929 6 Sheets-Sheet 2 JOHN HAYSHAMMOND JR.

ATTORNEY March 7,1933. HAMMOND JR 1,900,283

SELECTIVE RADIO'RECEPTION Filed Nov. 9, 1929 6 Sheets-Sheet 3 %I s1 v $1INVENTOR JUHN HAYS HAMMOND JR ATTORNEY Mairch 1933- J. H. HAMMOND, JR 1,2

SELECTIVE RAD I O RECEPTION Filed Nov. 9, 1929 e Sh eetS-Sheet 4INVENTOR 1mm HAYS HAMMOND m.

ATTORNEY March 1933- J. H. HAMMOND, JR

SELECTIVE RADIO RECEPTION Filed Nov. 9, 1929 6 Sheets-Sheet 5 wk C ww wINVENTOR JORN HAYS HMMOND JR.

ATTORNEY March 7, 1933. J. H. HAMMOND, JR

SELECTIVE RADIO RECEPTION Filed Nov. 9, 1929 6 Sheets-Sheet 6 L I f f is(i Patented Mar. 7, 1933 PATENT OFFICE JOHN HAYS HAMMOND, .13., FGLOUCESTER, MASSACHUSETTS snrnc'rrvn RADIO RECEPTION Application filedNovember 9, 1929. Serial No. 405,874.

The object of this invention is to supply an improved type of selectivesystem for radio communication.

It is a further object to obtain selectivity by the utilization of thespacial distribution of energy in radio transmission. These and otherobjects will become apparent from the following specification taken inconnection with the appended drawings.

A common feature of systems based on this invention is the spacialdistribution of energy representative of a transmitted signal, and areceiver gathering energy from different locations in a spacial sense.The spacial distribution of energy changes with time, and it is aproperty of the receiving system that only when the spacial distributionchanges in a proper manner with respect to time will the receiver systembe operated to give a signal. In accomplishing this invention, anantenna in the form of a transmission line,

several wave lengths long, is provided pointing in the general directionof the desired reception. At various intervals along the antenna,pick-up points are provided at which the energy existing in the antennaat said points is taken from the antenna. The energy thus picked up bythe various pick-up points is transmitted by land line to a central 0station where it is combined. The energy of the desired signal isarranged to combine in the proper phase while the energy of theundesired signal will not combine into a proper phase, and therefore, agreater degree of selectivity is obtained.

Having thus briefly described my invention, attention is invited to theaccompanying drawings in which:

Fig. 1 is a diagram illustrating the principle of the present invention.

Fig. 2 is a d'agram showing a. receiver for carrying out the presentinvention.

Fig. 3 is a modification of the receiver em- V bodying my invention inwhich a dummy antenna of the required length is substituted for theactual antenna inFig. 2.

Fig. 4 is a diagram showing the combining circuit for use in the centralreceiver of either Figs. 2 or 3.

Fig. 5 is a modification of the combining circuit shown in Fig. 4providing for shifting of the audio frequency phase.

Fig. 6 is another combining circuit arranged to reduce the noise levelefiects and utilize two beat type receivers. I

Fig. 7 is a diagram illustrating the wave distribution in the antennawhen two incoming waves are present.

Fig. 8 is a diagram illustrating the wave distribution along an antennawhen there are two waves present, one locally produced and one beingreceived from the transmitter.

Fig. 9 is a diagram showing the wave distribution for three phasereception.

Fig. 10 is a circuit for utilizing the distribution as shown in Fig. 8for phase opposition of modulation.

Fig. 11 is a circuit for utilizing 90 phase difference of modulation.

Having thus briefly described the figures embodying my invention,particular attention is now invited to Fig. 1, which shows anillustrative arrangement of the system embodying my invention, in whichthere is an antenna 10, and a counterpoise 11'of a length equal toseveral wave lengths of the radiations employed. The counterpoise andantenna are connected together at each end through resistances 12, whichact as terminal absorbers. The structure thus composed possesses theproperties of a transmission line. Ifthe signals proceed from left toright in Fig. 1,voltages represented by the curve 1 will exist acrossthe antenna and counterpoise.

With a certain continuous wave coming upon the line from thetransmitter, when a final steady state is reached there will be at anyinstant, voltagesacross the transmission line of different phase andmagnitude at different points. In particular at points A and B, at thesame instant of time the voltages may be opposed, with their. magnitudesomewhat different. If now the frequency of thetransmitted wave ischanged to another value or a wave of different frequency is received,the phase difference of the voltage at points A and B for that frequencywill, in general, not be inv opposition or of 0 180, but of some othervalue. 1

For example, with a continuous wave frequency of 10,000,000 cycles persecond and a propagation velocity along the line 3 X 10 centimeters persecond, at any instant of time the phase distribution along the linewill change by 360 electrical degrees in 30 meters of distance. Assumefor example that A and B are separated 615 meters,'so that there is atotal phase difference of 7380 electrical de rees for the 10,000,000cycle wave, corresponding to 41 half wave lengths. This actuates pick-upsystems at A and B in precisely the same manner as though the phasedifference were 180. degrees. Now let the frequency be altered slightly,say by onetenth of a percent, then the alteration of phases does notbecome .1 of 1 percent of 180, but .1 of 1 percent of 7380 or 7.38electrical degrees. Thus the use of a long transmission line permits alarge change of phase for a small percentage change in frequency. 7 Itis evident that for a large enough change of frequency, the number ofhalf wave lengths will change by an integral number, so that forexample, a phase difference of 180 degrees would exist for about10,500,000 or for about 9,500,000 cycles. Waves so far separated infrequency may however be prevented from interfering with the performanceof the system by simple tuning or band filtering methods.

A further understanding of the invention may be reached by considerationof the asrangement of Fig. 2 to which attention is now invited.

The antenna 10 and counterpoise l1 and resistances 12 are the same asthose shown in Fig. 1 except that the center point of the resistors 12are grounded at 13 as shown. Push-pull amplifiers 21, 22 and 23 areprovided for amplifying the energy picked up at the points A, B and Crespectively.

Here the voltage pick-up from the antenna 10 is shown from three points,A, B, C, at different locations on the transmission line, and the energyis transmitted to a central station 14 by suitable auxiliarytransmission lines 15 and 16. For a wave originating at A, the distanceto the central station 14 direct through the amplifier 21 differs fromthedistance to central station through amplifier 22 by the distance A toB, wherefore the 1 phase differences at the central station 14 will bethe same as between point A and B. When other points of pick-up are usedas at C, if desired a line or artificial line 17 from C to the centralstation 14 may be used equal in effective length to the distance from Aor B to the central station.

In place of an actual transmission line type antenna, the energy may bereceived in any type of antenna system, and impressed upon an artificialline with suitable design, such that the electrical phase shift persection of the artificial line is a different value for differentfrequencies. Such a line possesses the advantage of smaller spacerequired for the equipment, since by a lumped inductance and a lumpedcapacity, the phase difierence per section can be made the same as for alength of transmission line equal to nearly ahalf wave length. Such anarrangement is shown in Fig. 3, in which the energy is received by theantenna system and amplified by the amplifier 31 and put into theartificial line, with pick-off circuits 32, 33 and 34 to a commonreceiving system 35.

It is evident that the feature in common between Figs. 2 and 3 is amethod of producing voltages from an incoming signal from differentpoints in space, and leading them into a common receiving system.Further the number of pick-up points may. be as many as desired, and theterminals may be utilized in any number of ways.

One mode of utilization of the various channels produced from a givensignal is shown in Fig. 4. This circuit may be used in connection witheither Fig. 2 or Fig. 3.

For this figure it is assumed that points A, B andC, have been chosen insuch a manner that all voltages of the desired frequency are in phase.Leads 43, 44, and 45 from individual pick-up points are brought togridfilament branch of combining tubes 40, 41 and 42 respectively, butthe plate circuits of the combining tubes are in parallel with a commonoutput inductance 46 inductively related to a second inductance 47 inthe input of a usual type radio amplifier and receiver and indicator. Inthis manner, the desired signals are built up in strength much morerapidly than undesired signals, because the desired signals of equalphase add on a voltage basis, whereas interferences being of randomphases combine on an energy basis.

The central station may contain phase shifting devices whereby thephases of the desired signals may be correctly lined up previous tocombining. This modification is shown in Fig. 5 in which the terminals50, 51 and 52 go to individual amplifiers as shown, each operating intoa phase shifter 56 of well-known construction. The outputs of the phaseshifters are impressed upon the grid circuits of the combining tubes 57,through a suitable arrangement for controlling volume such as thepotentiometers 58. The output of the combining tubes is the same as inFig. 4.

Thus the utilization systems shown above involve the idea of combiningthe plurality of desired voltages from various pick-up points in themost advantageous manner, for the purpose of building up the desiredsignal in a much more efficient manner than the in, terfering signalswill be built up.

Another utilization method for the reception of continuous wave signals,which method involves the reduction of noise level efiects, is shown inFig. 6. In this arrangement three pick-up points may be used withadjustments made so that voltages due to the desired signal at A and Bare made equal but oppositely phased.

Referring now more particularly to Fig. 6, the inputs from the threepick-up points are indicated at 60, 61 and 62 which go to individualamplifiers 68, 64 and 65 in the same manner as in Fig. 5. The outputs ofeach of these amplifiers operates into a phase shifting circuit 66 andthe intensity of the output is regulated by the potentiometers 68 andfed to amplifier devices 67, 67 and 67 The outputs from 67 and 67arerepresentative of the voltages at points A and B respectively, and arecombined out of phase with respect to the desired signal in theinductance 69. Two heat type receivers and 71 are provided, the formerof which is supplied by the inductance 69 and the latter of which issupplied by the output of the amplifier 67 representative of the energyat the point C. These two receivers are both supplied with a commonheterodyning frequency by the source .72. The receiver 70 will thusreceive only the interference, the signal having been balanced out, andthe receiver 71 will receive the interference and the signal.

The output of each of the receivers 70 and 71 is fed to a rectifier 72and 7 3 respectively, of the power type. In the power circuit of each'ofthe rectifiers there are resistors 74;, which resistors are connected inseries with each other and with the coil 75 of relay 76.

The receivers thus operate in well-known manner to produce audiocurrents, and stray interference noises. These are rectified by powertype rectifiers. The rectified outputs of each channel are balancedagainst each other, and adjustments made such that with no incomingsignal the rectified currents due to stray disturbances will completelycancel.

Then with the incoming signal present there will be an increase ofrectified current through one channel overthat in the other channel,with a difierent potential drop across the resistors carrying therectified currents. This will cause current to flow through theindicating relay.

In another type of application of this invention, the signals tobereceived may not be continuous waves, but maybe modulated, orotherwise varied, radio waves. Or the modulations may be of so high afrequency that the radiations may be thought of as two or more distinctwave lengths. .In any case, the phase of the beats or modulations willbe different at diiferent points on the line.

Fig. 7 for example, shows the transmission line composed of antenna 10and counterpoise 11 as in Fig. 1, the curve 7 7 representing thevoltages at the various points with two continuous waves from atransmitter. The pick off points A and B are'chosen to be in phaseopposition of modulation. 7 Further in place of two incoming continuouswave signals, it may be desirable to use butone incoming signal, and alocal oscillator, in which case a modulated distribution will occuralong the line, the same as though two waves were radiated from thetransmitter. Fig. 8 shows a curve similar to curve 77 of Fig. 7representative of this condition.

In either case, points can be chosen with definite phase relation of themodulation cycle, as for example such that 180 phase difierence willexist in the modulation, and therefore 180 difference in the-currentproduced when the radio signals are subj ected to detection. 7

In a still further arrangement, three points might be used, with 120difference of phase in the modulation, as shown in Fig; 9, in whichcurve is the same as curve 77 of Fig. 7 and the points A, B and C are120.

from each other with respect to the phase of modulation.

Two points with 90 phase difference, or a plurality of points with 90phase difference may also be used.

As numerical example, with a propagation velocity of 3 X 10 centimetersand an incoming signal of 30 meters or 10,000,000 cycles, and aheterodyning signal of 9,500,000

cycles togive an intermediate frequency of 500,000 cycles, themodulation pattern will be recurrent in 19 of the 9,500,000 cycle wavelengths, or 20 of the 10,000,000 cycle wave lengths, that is in 600meters of line. Or for 10,000,000 cycles incoming signal, and 8,000,-000 cycles heterodyne, the modulation pat tern will be recurrent in fiveof the 10,000,000 cycle wave lengths, and'four of the 8,000,000 cyclewave lengths, that is in 150 meters of line; or with suitable artificialline, in the latter case the modulation pattern will be recurrent in tento fifteen sections.

A circuit for utilizing phase opposition of modulation as in Fig.8, isshown in Fig. 10 to which attention is now invited. Here the pick-offpoints A and B lead to individual push-pull detectors 81 and 82respectively, by non-oscillating beat detection, since the heat wave hasbeen transmitted from the recording station, or has been produced on thetransmission line by combininga local oscillator with the incomingsignal. The detected currents are subsequently selected as for exampleby tuned circuits 83 and 84. Due to the difference of modulation phase,the se lected currents will be in phase opposition, and may be combinedfor further utilization by reversed or differential couplings as shown.Subsequent to combining the signals may be reduced to audibility bymeans of a second order detector 85 and separate heterodyne 72.

It is to be understood that several additional pick-up points may beused to improve the ratio of building up of signals to the ratio ofbuilding up of stray interferences. Further the type of receiver may bealtered in many ways, such as by insertion of amplifiers, etc.

Attention is now particularly invited to Fig. 11 which shows a circuitfor utilizing a 90 phase difference of modulation. Here the curve 80represents the heat wave form produced by the incoming signal or theheterodyning of the incoming wave and a local frequency. There are shown8 pick-up points each of which has an individual high frequencyamplifier and detector 91, to produce currents of the difference of theincoming and locally supplied high frequency or in other words, theintermediate frequency. The output of the detectors and amplifiers 91 ispicked up by the pick-up inductances 92, 93, 94 and 95 in such a mannerthat inductances 92 and 93 are arranged in series, the latter beingreversed to supply the input of the second detector 96 and theinductances 94 and 95, the latter of which are reversed to the former,are connected in series and are adapted to supply the input of thesecond detector 98. The detectors 96 and 98 are of the beat frequencytype, being supplied by the common heterodyning source 97. As a result,a low frequently two phase current is produced in the outputs 99 and100. Each of the two phases existing in 99 and 100 is led to theappropriate windings of a two phased relay shown generally at 101, whichis similar to a two phase induction motor with an armature 102 whichmoves only when two phases are present. Thus when the proper two phasecurrent exists in the windings of the relay 101, or in other words, whenthe incoming signal is present, the armature 102 will be oscillated toclose the contacts 103 and 104 and thus operate a receiving circuit. Inthis manner the relay is operated when an incoming signal is present andthrough the combined use of spacial distribution and intermediatefrequency tuning and two phase relay operation, and an extremely highdegree of selectivity is obtained.

Having thus described the various forms or embodiments of my inventionas well as their operation, attention is invited to the fact that agreat many modifications may be suggested which fall into the scope ofthis invention. Therefore, it is to be understood that I am not to belimited by the specific embodiments shown and described for the purposeof illustration only but by the scope of the invention as defined in theappended claims.

What I claim is:

1. The method of radio reception which includes producing a spacialdistribution of the energy representative of a radio signal within aclosed path, and combining the energy thus distributed along points ofthe path where the signal is in the proper phase when of the desiredfrequency, and not in phase when of an undesired frequency.

2'. The method of radio reception which includes distributing the energyrepresentative of a radio signal along a closed path in such a mannerthat various phases of the frequencies of which said frequency iscomposed are available, and combining the energy thus distributed fromseveral points along said path in such a manner that signals of thedesired frequency will be in phase, and signals of undesired frequencywill be not in phase.

3. The method of radio reception which includes analyzing the voltagesproduced by a signal being received along a closed path, and combiningthe voltages thus analyzed as derived from several points along saidpath to be in phase when of the desired frequency representative of thedesired signal, and to be not in phase when of an undesired signal.

4. The method of continuous wave reception which includes heterodyningthe incoming signals to produce a modulated wave, distributing theenergy representative of said modulated wave in a spacial manner,picking up energy representative of the various phases of modulation ofsaid modulated wave thus distributed, amplifying and detecting saidenergy to produce a plurality of currents of a frequency equal to thedifference of the local and incoming signals, combining energies of thesame phase to produce polyphase sources of the difference frequency,generating a lower frequency, detecting each phase of said producedpolyphase difference frequency by heat detection with said lowerfrequency to produce a lower frequency polyphase current, and operatingan indicating device by said last mentioned current.

5. The method of continuous wavereception which includes heterodyningthe incoming signals to produce a modulated wave of a high order offrequency, distributing the energy representative of said modulated wavein a spacial manner, picking up energy representative of the variousphases of modulation of said modulated wave thus distributed, amplifyingand detecting said energy to produce a plurality of currents of afrequency equal to the difference of the local and incoming signals,combining energies of the same phase to produce polyphase sources of thedifference frequency, generating a lower frequency, and detecting eachphase of said produced polyphase difference frequency by beat detectionwith said lower frequency to produce a low frequency polyphase current.

6. The method of continuous wave reception which includeslocallyheterodyning the incoming signalsto produce a modulated wave,analyzing the energy representative of said modulated wave, combiningenergy representative of the various phases of modulation of saidmodulated wave thus analyzed, amplifying and detecting said energy toproduce a plurality of currents of a frequency equal to the differenceof the local and incoming signals, combining the energies of the samephase to produce polyphase currents of the "difference frequency,detecting each phase of said produced polyphase dif ference frequency bybeat detection to produce a lower frequency polyphase current, andoperating an indicating device by said last mentioned current.

7. The method of high frequency modulated continuous wave receptionwhich includes distributing the energy representative of said modulatedwave in a spacial manner, combining energy representative of the variousphases of modulation of said modulated wave thus distributed, amplifyingand detecting saidenergy to produce a plurality of currents of afrequency equal to the modulation frequency and representative of thephases thereof, combining the energies of the same phase to producepolyphase sources of difference frequency, generating a lower frequency,detecting each phase of said produced polyphase difierence frequency bybeat detection with said lower frequency to produce a lower frequencypolyphase current, and operatin an indicating device by said lastmentioned? current.

8. The method of continuous wave reception which includes distributing amodulated wave representative of a high frequency carrier and anotherfrequency in a spacial manner, picking up energy representative of thevarious phases of modulation of said wave,

and thus producing a plurality of currents of the modulation frequency,combining the currents of the same phase, generating a lower frequency,detecting each phase of said modulated energy by heat detection withsaid lower frequency and thus producing a lower frequency polyphasecurrent and operating an indicating device by said current.

9. In a radio receiver,'means for receiving incoming signal energycomprising an antenna system having an electrical length greater thanone wave length of the signal energy desired to be received, means fordistributing said incoming energy in a spacial manner, a plurality ofmeans for picking up energy representative of the various phases of theincoming frequency, and means for combining the energy thus picked up inphase when of the desired fre-.

quency, and not in phase when of an undesired frequency. v

10. In a radioreceiver, means for receiving incoming signal energy,means for distributing said incoming energy in a spacial manplurality ofmeans for picking up energy representative of the various phases of the1ncoming frequency, means for amplifying the energy thus picked up, andmeans for com ,bining theenergy thus amplified in phase when of thedesired frequency, and: not in phase when of an undesired frequency.

l1. Ina radio receiver, means for receiv: ing the incoming energy, meansfor distributing said incoming energy in a spacial manner, a pluralityof means for picking up energy representative of the various phases 'ofthe incoming frequency, means for regulating the intensity of the energythus picked up, and means for combining the said energy in the properphase when of the desired frequency, and not in phase when of anundesired frequency comprising a plurality of electron discharge deviceshaving their input circuits connected respectively to said means forpickirig pp energy andtheir output circuits in para le 12. Apparatus forthe reception of radiant energy in the form of high frequency modulatedcontinuous frequency comprising means for receiving energyrepresentative of the desired signal, means for distributing the energyrepresentative of said desired signal in a spacial manner, a pluralityof pick-up points for tapping energy representative of the desiredsignal in its variousphases of the modulation frequency, means foramplifying and detecting the energy picked up at each of said points andthus produce a plurality of currents of a frequency equal to themodulation frequency but of different phase, means for combining saidcurrents of the same a common heterodyning source of low frequencyenergy, means for producing a polyphase current by the heterodyne detection of said currentsv representative of the modulation'frequency, andmeans for operating an indicating device by the polyphase low frequencyenergy thus produced.

13. Apparatus for the reception of radiant energy including, means forreceiving energy phase,

representative of the desired signal, means for distributing the energyrepresentative of said desired signal in a spacial manner, a pluralityof pick-up points for tapping energy representative of the desiredsignal in its means for amplifying and detecting the energy picked up ateach of said points and thus produce a plurality of currents of afrequency equal to the modulation frequency but of different phase,means for combining said cura signal. 1:}

various phases of the modulation frequency, 1120 14. In a radioreceiver, means for receiving incoming signal energy comprising amultisect-ion artificial line wherein signal energy is intercepted atone end thereof and made to flow along said line, said artificial linehaving an effective electrical length at least equal to one wave lengthof the signal energy desired to be received, a plurality of means forpicking up energy representative of the various phases of the incomingsignal energy along various sections of said line said energy pick-upmeans being coupled to said line at various points thereof such that theenergy picked up thereby is in phase when of the desired frequency andout of phase when of undesired frequency.

JOHN HAYS HAMMOND, JR.

